An acrylic polymer obtained by polymerization using a special polymerization catalyst is disclosed in Patent Document 1. Patent Document 1 also discloses a curable composition composed of such a special acrylic polymer and a silane coupling agent. However, the curable composition is still poor in, for example, adhesion properties and rubber-like properties.
On the other hand, room temperature-curable compositions containing crosslinkable silyl group-containing organic polymers have already been industrially produced, and have been widely used for sealants, adhesives, coating materials, and the like. In general, these curable compositions contain various metal catalysts so as to have curability. The kind of metal catalyst to be used and the amount thereof to be added are varied depending on the purpose of use of the curable compositions.
As such catalysts, reaction products of organotin compounds with ester compounds have been conventionally known (see, for example, Patent Documents 2-5). Particularly, catalysts obtained by using phthalate esters as the ester compounds have been generally used. However, the phthalate esters are volatile organic compounds (VOC) whose guideline values have been specified by Ministry of Health, Labor and Welfare, and the use of the phthalate esters is being perceived as a problem. In recent years, it is therefore desired that catalysts be designed without using the phthalate esters.
Meanwhile, there have been high market demands for quickly-curable products, but such quickly-curable products have a disadvantage that they are cured in course of production. For example, Patent Document 5 discloses an organic polymer containing a crosslinkable silyl group represented by —SiX3 and a curable composition containing a reaction product of dialkyltinoxide with an ester-based compound. However, such a curable composition has caused a problem that products are cured in course of production due to its high reactivity. In a case where an organotin compound-based curing catalyst having a relatively low reactivity is used in view of production stability, quick curability cannot be attained. On the other hand, in a case where an organotin compound-based curing catalyst having a relatively high reactivity is used in view of quick curability, production stability cannot be attained as is the case with the product containing a reaction product of dialkyltinoxide with an ester-based compound.
Recently, equipment which can produce catalysts in a completely enclosed system has been developed, and is being well received by manufacturers of room temperature-curable products. However, introduction of such equipment involves some problems that there is a limit to the number of additives and the equipment is very expensive. Under the circumstances, the present inventors have intensively investigated an organotin compound-based curing catalyst which can exhibit high activity after a certain length of time has elapsed, which has led to the completion of the present invention.
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-40037
Patent Document 2: Examined Japanese Patent Application Publication No. 1-58219
Patent Document 3: Japanese Patent No. 3062625
Patent Document 4: Japanese Patent Application Laid-Open No. 8-337713
Patent Document 5: Japanese Patent Application Laid-Open No. 2003-138151
Patent Document 6: Japanese Patent Application Laid-Open No. 11-12480
Patent Document 7: Japanese Patent Application Laid-Open No. 52-73998
Patent Document 8: Japanese Patent Application Laid-Open No. 55-9669
Patent Document 9: Japanese Patent Application Laid-Open No. 59-122541
Patent Document 10: Japanese Patent Application Laid-Open No. 60-6747
Patent Document 11: Japanese Patent Application Laid-Open No. 61-233043
Patent Document 12: Japanese Patent Application Laid-Open No. 63-112642
Patent Document 13: Japanese Patent Application Laid-Open No. 3-79627
Patent Document 14: Japanese Patent Application Laid-Open No. 4-283259
Patent Document 15: Japanese Patent Application Laid-Open No. 5-70531
Patent Document 16: Japanese Patent Application Laid-Open No. 5-287186
Patent Document 17: Japanese Patent Application Laid-Open No. 11-80571
Patent Document 18: Japanese Patent Application Laid-Open No. 11-116763
Patent Document 19: Japanese Patent Application Laid-Open No. 11-130931
Patent Document 20: Japanese Patent No. 3313360